1. Field of the Invention
The instant disclosure relates to a drive device; in particular, to a light emitting element drive device.
2. Description of Related Art
Light-emitting element, such as a light-emitting diode (LED), could be utilized as a back light source of the display as well as a display element. The brightness of the LED could be increased due to increasing of the current flowing through the LED. A plurality of light-emitting strings with the same current in each light-emitting string could be applied to provide a uniform light source.
Usually, the light-emitting string is composed of a plurality of light-emitting elements (e.g. LEDs) which are serially connected. A terminal of the light-emitting string receives a driving voltage and another terminal of the light-emitting string is coupled to a current source. When the conducting voltages of the light-emitting strings are the same, each of the same current sources could be utilized to provide the same current to each of the light-emitting strings, such that each light-emitting string could emit light with the same brightness.
However, the light-emitting elements with the same design may have different conducting voltages due to the process variation of manufacture, thus each light-emitting string may have different conducting voltage. Depending on the existing technology, the light-emitting strings for the back light source are coupled to the same driving voltage, in which the light-emitting string with larger conducting voltage may cause the voltage at the terminal of the light-emitting string which is coupling to the corresponding current source to be too low, such that the corresponding current source would not operate normally.